1. Field of the Invention
This invention relates to column chromatography. In particular this invention relates to the structure of chromatography columns and methods for sealing the ends of such columns in specifically designed holder assemblies to provide leak-proof connection to high pressure fluid lines.
2. Description of the Prior Art
Chromatography in general and high pressure liquid chromatography (HPLC) in particular are widely used for analytical and preparative separations of mixtures of chemical species. For optimum accuracy and efficiency as well as safe operation, the sealing of the separation column into the remainder of the apparatus is a serious concern. This concern is particularly acute in HPLC due to the high pressures involved, which generally range from about 1,000 to about 10,000 psi.
The seal which is most frequently connected and disconnected by the user is that between the column and the tubing which connects it to the rest of the apparatus (which includes a high pressure pump, liquid transfer lines, etc.). The user frequently removes and replaces the column from one separation to the next in order to adapt the apparatus to accommodate a range of mixtures. This is generally accomplished by using a seal which is capable of being assembled and disassembled repeatedly by the user. The use of compression fittings with metal-to-metal contact is prevalent in the equipment currently available. Examples of such fittings are those manufactured by Crawford Fitting Company of Cleveland, Ohio (sold under the trademark "Swagelok") and a similar seal made by Parker-Hannifin, also of Cleveland, Ohio. The disadvantage of such fittings is that they are expensive and are usable only a limited number of times before their sealing capacity is lost and replacement is necessary. Furthermore, these fittings must be assembled with the use of tools, and require considerable manual dexterity on the part of the user to effect a connection to the chromatography system. Additionally, some columns and their packings exhibit short lifetimes and must be frequently replaced in order to obtain acceptable performance of the apparatus. Low cost, disposable column systems with reusable cartridge holders overcome the disadvantages and inconveniences of conventional HPLC columns and column fittings. Examples of HPLC cartridge systems are those manufactured by CHROMPACK of Bridgewater, N.J. and Brownlee Labs of Santa Clara, Calif.